Electrical Power Generation and Architecture Structure for Controlling an Acoustic Fire Suppression System

ABSTRACT

An electrical scheme and architecture intended for a Fire Suppression System utilizing resonant or impulsive acoustic waves. The system is capable of surviving within an active wildfire environment and harvesting energy from the fire to power itself or actively diverting thermal energy for temporary cooling. The electrical systems optimize and modulate the fire suppression acoustic wave output for the changing ambient environment and actively tune the system to reduce power requirements.

REFERENCE TO RELATED APPLICATIONS

This application claims priority to the U.S. provisional application No. 63/317,506 filed on Mar. 7, 2022.

SUMMARY OF THE INVENTION

Described herein is an Electrical Power Generation and Architecture Structure for Controlling an Acoustic Fire Suppression System. This system may be mounted statically or stationarily, deployed from a vehicle, or incorporated into a complete unmanned vehicle (which may be autonomous or remotely operated). The unmanned vehicle version of this technology may be ground based, aerial, or aquatic.

The Fire Suppression System is configured to survive within an active wildfire environment, and potentially harvest energy from the fire to power itself. The primary mode of fire suppression is a pressure impulse or acoustic wave generated within the Fire Suppression System, which may be called an “Acoustic Cannon.”

The electrical systems may be designed to passively or actively control the acoustics and power generation. An active control configuration would require that the electrical components are cooled, whereas a passive control configuration may enable high temperature Silicon Carbide (SiC) components to be used, avoiding the need for cooling.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block Diagram for Fire Suppression System with Thermoelectric Power Generation;

FIG. 2 is a block Diagram for Fire Suppression System with Thermophotovoltaic Power Generation;

FIG. 3 is a block diagram for Fire Suppression System with Stirling Power Generation;

FIG. 4 is a block diagram of Electrical System Positioning Within System;

FIG. 5 is a schematic example of Zener Controller;

FIG. 6 is a schematic example of a Battery Charging Circuit;

FIG. 7 is a schematic example of Safety Circuit;

FIG. 8 is a schematic example of Piezoelectric Driver;

FIG. 9 is a schematic example of Magnetostrictive Driver; and

FIG. 10 is a schematic example of Electro-mechanical Driver.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The Command Module is responsible for controlling the complete Fire Suppression System, and each of the subsystems including any combination of subsystems including onboard thermal energy conversion, power distribution, load balancing, battery charging with safeties??, propulsion, navigation, communications, and tuning for energy harvesting and the fire suppression system, while ensuring that each of the subsystems interacts appropriately. FIG. 1 , FIG. 2 , and FIG. 3 show two variations of a portion of the Command Module block diagram which pertain to the power generation and distribution systems.

One embodiment of the invention, shown in FIG. 1 , utilizes a thermoelectric generator (2) as the thermal energy generation source for the system. In this embodiment of the invention, the hot side of the thermoelectric generator is sufficiently heated by the external ambient environment, such as in a wildfire (1) and the cold side of the thermoelectric generator is kept cold by a Coolant Storage Tank (3). A thermal gradient causes a Direct Current (DC) power output to the electrical system (4). Subsequently, as shown in FIG. 1 , a tuning module, located at the temperature-controlled interior of the system (FIG. 4 ), is utilized to vary the resistive load perceived by the thermoelectric generator. This optimizes the power output efficiency of the thermoelectric generator based on the temperature gradient, the battery charge level, and the load being drawn by the propulsion and fire suppression systems. The tuning module, as shown in FIG. 1 , senses the power input from the thermoelectric generator and/or power output with a current sensor (6), as shown in FIG. 6 , and adjusts the resistive load regularly to achieve peak current flow. The tuning module may be a Zener controller, as shown in FIG. 5 , resistive load bank, or a variation of a trim pot that is adjustable electronically. The Zener control will utilize comparator circuits with operational amplifiers that add resistors as voltage limits are surpassed. A load balance module is utilized as a method for adding a load above what is needed for optimal thermal to electric conversion to the thermoelectric generator if the battery, propulsion, and fire suppression systems are not drawing enough power to maintain a safe temperature, around 850 C, for the hardware, and the hot end of the thermoelectric generator is becoming too hot. A temperature feedback, utilizing temperature sensors such as thermocouples, infrared devise, or thermistors, is available to the Load Balance Module (not shown) for the autonomous determination of required load. The Charging Module is shown in FIG. 6 . This charging circuit utilizes a DC-DC convertor (5) to match the thermoelectric generator output voltage with the optimal voltage for battery charging. The current sensor (5) works with the operational amplifiers in a comparator circuit (7) to maintain constant current in the charging cycle. The Safety Module is shown in FIG. 7 disables battery charging if the battery is fully charged, as determined by the slope of voltage change, or if the battery is becoming overheated, such is determined by thermistors mounted to the battery. A second tuning module is used to condition the power output from the battery to the Acoustic Cannon (not shown). Power conditioning for the Acoustic Cannon includes DC to AC conversion utilizing Pulse Width Modulation (PWM) at the operating frequency and is driven through a reactive power conditioner, a part of the second tuning module, shown in FIG. 1 .

For optimal performance of a driver, the attached electrical circuit needs to provide the appropriate impedance, which essentially provides an electrical spring by shifting the voltage-current phasing in the Alternating Current (AC) through complex impedance. This electrical spring is called reactive power, and the attached circuit is called a reactive power conditioner. The reactive power conditioner t introduces the complex impedance is shown in Formula 1, where z is the impedance, x is the real resistance and y is the imaginary resistance, letting j=√{square root over (1)}:

z=x+jy  Formula 1:

The reactive power conditioner, a component of the tuning module, is a capacitive element in the case of both an electro-mechanical driver (FIG. 10 ) and magnetostrictive driver (FIG. 9 ). Alternatively, the reactive power conditioner is an inductive element in the case of a Piezoelectric driver (FIG. 8 ). The reactive power conditioner is meant to counteract the imaginary portion of the AC power signal. Operating frequency of the acoustic cannon is determined using temperature and pressure sensors (not shown) to determine the appropriate wavelength in ambient conditions. Propulsion power is directed via the logic within the Command Module (not shown) and by using feedback from accelerometers (not shown) in the unit.

Alternatively, a thermal energy conversion system utilizing thermophotovoltaics may be used in place of the thermoelectric power generation, shown in FIG. 2 . The thermophotovoltaic system would function identically to the operation of the thermoelectric system, shown in FIG. 1 , described above but would capture photons generated by the fire and convert them to usable electrical power, much like a high temperature solar cell.

In the case of a Stirling power generation, shown in FIG. 3 , the electrical systems function identically to those of the Thermoelectric powered system, with a couple exceptions. The power provided from a Stirling device, free-piston or thermoacoustic, would be provided in an AC signal and need to be converted to DC, as shown in FIG. 3 . The tuning circuit for the Stirling convertor would consist of capacitors, rather than resistors. Furthermore, an active system cooling is achievable through a purposeful de-tuning of efficiency. If the thermal energy system hot end begins to reach an above-desired temperature as determined by a pre-programmed algorithm, the tuning circuit can tune the impedance such that the system runs with lower thermal-to-electrical efficiency. The effect of this action is to force a larger heat flow through the thermal energy conversion device, consequently lowering the hot end temperature. This can allow a colder temperature operation, though power output would be restricted in this mode.

For the above-described control strategies, all active components would require cooling, which can easily be provided by the Coolant Storage Tank (4). However, this will limit the mission life. Alternatively, the above-described electrical components may be substituted for or comprise Silicon Carbide (SiC). Utilizing SiC components will increase the allowable working temperature within portions of the Command Module (not shown), reducing the amount of cooling required for the electrical systems and extending mission life.

Additional embodiments of the above-described control methodologies are achievable with active electrical systems, rather than passive elements. Namely, the tuning portions of the controller may be replaced with control logic that vary the voltage-current phasing to achieve changes in perceived impedance like capacitors or inductors. This method is known to those skilled in the art as synthetic capacitors or synthetic inductors but is novel in its use described herein. 

What is claimed is:
 1. A command module for controlling a Fire Suppression System and any combination of subsystems including onboard thermal energy conversion, power distribution, load balancing, battery charging with safeties, propulsion, navigation, communications, and tuning for energy harvesting and the fire suppression system, while ensuring that each of the said subsystems interacts appropriately.
 2. The command module of claim 1 further comprising a Thermoelectric Generator to convert energy from the ambient environment to power the Fire Suppression System.
 3. The command module of claim 2 further comprising a first tuning module to vary the resistive load perceived by the thermoelectric generator using a Zener controller, resistive load bank, or a trim pot that is adjustable electronically.
 4. The command module of claim 1 where the first tuning module senses the power input from the thermoelectric generator and/or power output with a current sensor.
 5. The command module of claim 1 further comprising a load balance module for adding supplemental resistive load to the thermoelectric generator if the battery, propulsion, and fire suppression systems are not drawing electrical power sufficient to maintain a safe temperature for the hardware, and the hot end of the thermoelectric generator is becoming too hot, above an operating temperature around 850 C, using temperature feedback to the Load Balance Module for the autonomous determination of required load.
 6. The command module of claim 1 further comprising: a. a charging circuit with a DC-DC convertor to match the thermoelectric generator output voltage with the optimal voltage for battery charging, b. a current sensor which works with the operational amplifiers in a comparator circuit to maintain constant current in the charging cycle, and c. a safety module that disables battery charging if the battery is fully charged, as determined by the slope of voltage change, or if the battery is becoming overheated.
 7. The command module of claim 1 further comprising (a) a second tuning module to condition the power output from the battery to the Fire Suppression System for power conditioning of the Fire Suppression System for DC to AC conversion, and (b) a Pulse Width Modulation at the operating frequency and which is driven through a reactive power conditioner, the reactive power conditioner being (i) a capacitive element in the case of both an electro-mechanical driver and magnetostrictive driver, or (ii) an inductive element in the case of a Piezoelectric driver.
 8. The command module of claim 1 further comprising temperature and pressure sensors for determining operating frequency of the acoustic cannon based on the appropriate wavelength in ambient conditions.
 9. The command module of claim 1 further comprising accelerometers to direct propulsion power based on acceleration data.
 10. The command module of claim 1 further comprising a thermal energy conversion system utilizing thermophotovoltaics for providing system or subsystem power.
 11. The command module of claim 1 further comprising a thermal energy conversion system utilizing at the Stirling cycle for providing system or subsystem power.
 12. The command module of claim 1 further comprising SiC components to increase the allowable working temperature within portions of the Command Module, reducing the amount of cooling required for the electrical systems and extending mission life. 